Disc-sealed electron discharge tubes

ABSTRACT

A disc-sealed electron discharge tube wherein the grid electrode or electrodes and a hollow anode each have a flat surface provided with an annular slot for the passage of electrons, radial spoke-like elements extend across said slots, the radial elements in each electrode being aligned with the radial elements in the other such electrodes, and wherein means are provided to magnetically focus the hollow electron beam.

United States Patent L 9 Heynis ch et a1.

[ DISC-SEALED ELECTRON DISCHARGE TUBES [75] Inventors: l-linrichHeynisch, Graefelfing; Josef Kellerer; Walter Schneider, both of Munich,all of Germany I [73] Assignee: Siemens Aktiengesellschaft, Berlin &

Munich, Germany [22] Filed: Oct. 13, 1972 [21] Appl. No.: 297,339

[30] Foreign Application Priority Data 'Nov. 2, 1971 Germany 2154485[52] U.S. Cl 315/39, 315/531, 315/538,

' 313/45 [51] lnt.'Cl H01j 7/46, l-lOlj 19/80 [58] Field of Search315/529, 5.31, 5.38, 39; 333/13; 313/45 [56] References CitedUNITEDSTATES PATENTS Harris 3l5/5.31 X

[4 1 Mar. 19, 1974 3,453,482 7/1969 Preist 315/538 X 3,527,981 9/1970Hopper, Jr. et al 315/39 3,139,552 6/1964 Brewer 315/529 X 3,388,2816/1968 Clement Arnaud 315/538 X 3,259,790 7/1966 Goldfinger 315/538 XPrimary Examiner-James W. Lawrence Assistant ExaminerSaxfield Chatmon,Jr.

Attorney, Agent, or Firm-l'1ill, Sherman, Meroni, Gross & Simpson [5 7]ABSTRACT A'disc-sealed electron discharge tube wherein the gridelectrode or electrodes and a hollow anode each have a flat surfaceprovided with an annular slot for the passage of electrons, radialspoke-like elements extend across said slots, the radial elements ineach electrode being aligned with the radial elements in the other suchelectrodes, and wherein means are provided to magnetically focus thehollow electron beam.

6 Claims, 1 Drawing Figure BACKGROUND OF THE INVENTION 1. Field ofthelnvention This invention relates to disc-sealed electron dis- 4charge tubes which are capable of high-power output at ultra-highfrequencies, of the kind comprising an annular metal-capillary cathodehaving a central nonemissive area of lower temperature than the emissiontemperature prevailing in the emissive area and responsible forproducing a hollow electron beam, one or more grid electrodes and ananode which has an annular active end area to receive the electroncurrent.

2. Description of the Prior Art The present invention is particularlyuseful for the generation of ultraffrequencies of the order of a fewGC/sec and is applicable both to triode and tetrode types of electrontubes. The quality and quality factors of disc-sealed tubes, both oftriode-and tetrode constructions, have undergone considerableimprovement ferred to above, the possibilities which are open togenerate high powers using grid-control tubes are limited, in particularby the increase in size of the overall system. Because the dimensionsmust be kept as small as possible in grid-control tubes compared withthe wave length, a disadvantage arises in that a limit is reached which,in power output tubes, is set in particular by the grid, loading of thetube. This makes it necessary to change from the cross-braced type gridto some other type of system. A further increase in power can then onlybe achieved byincreasing the current density and the operating voltages,while at the same time retaining the major tube dimensions. This kind ofprocedure, however, encounters a limitation in terms of the thermalloading capacity of the anode material.

' A disc-sealed tube having a dispenser metal-capillary cathode whichhas an annular emissive area and produces a hollow electron beam is wellknown in the art, but in this type of tube the grid electrode isdesigned to extend over the full circular area as a cross-braced grid,and the active part of the solid anode is designed as a flat reflectoranode. In the known construction of a disc-sealed tube, the output poweris limited by the specific loading capacity of both the grid electrodeand the anode.

SUMMARY OF THE INVENTION An object of the present invention, therefore,is to provide a power increase by increasing the discharge currentdensity, by special design of the critical electrodes, and by additionalcontrol of the electron beam, such as may be effected by magneticfocusing.

The invention resides in the provision of a disc-sealed electrondischarge tube of the type mentioned above, wherein the grid electrode,or electrodes, and a hollow anode each have a flat surface provided withan annular slot for the passage of electrons. Radial spoke-like elementsextend across the slots to support the central portions of theelectrodes, the radial spoke-like elements in each electrode beingaligned with the radial spoke-like elements of the other electrode orelectrodes. Further, means are provided for magnetically focusing thehollow electron beam.

When using a hollow anode, the beam energy can be distributed over asubstantially larger area by suitable additional focusing measures. Theanode therefore preferably comprises a hollow cylinder which extendsbeyond the surface and provided with an annular slot, and the outer wallof which cylinder is provided with a convection cooler.

In order to dissipate the grid loss power by conduction and heattransfer, e.g., by utilizing cooling air, it is preferable for the gridelectrode, or electrodes, to have a cup-shaped form, the controllinggrid surface being substantially solid for reasons of stability and goodthermal conductivity, so that only an annular portion thereof,comprising radially extending grid elements, actually serves as theactive grid electrode. For this purpose, and to facilitate and makepossible suitable magnetic focusing, parts of the grid and anodeelectrodes which are not directy involved in the discharge, andneighboring parts of the discharge vessel wall, in the neighborhood ofthe focusing magnet or coil, are preferably made of magnetic material.

In order to exploit the full power capacity of the tube, and to providean easily exchangeable component which can be used in an amplifier, itis advantageous to make the tube part of a single unit including anassociated tank circuit, a cooling arrangement and a magnetic focusingarrangement.

BRIEF DESCRIPTION OF TI-IE'DRAWING Other objects, features andadvantages of the invention, its organization, construction andoperation will be best understood from the following detaileddescription of a preferred embodiment of the invention taken inconjunction with the accompanying drawing on which a single FIGURE of adisc-sealed triode is illustrated in a generally elevational crosssectional showing. Components which do not form an essential part of theinvention are left unmarked or are omitted from the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT A metal-ceramic tube isillustrated in the drawing as a disc-sealed triode having an annularmetal-capillary dispenser cathode I of low operating temperature. Thecathode comprises a ring-shaped porous emission substance carrier disc 2which covers and closes off a correspondingly shaped dispenser and formsthe emissive cathode body. Beneath the cathode body and inside anassociated carrier foil cylinder 3, there is arranged a heater 4 whichis, for example, cemented in position.

In the central hollow cylinder of the cathode body 2, and at the endfacing the grid electrode 5, there is provided a radiation protector orfoil 2' which takes the form of an outwardly dished sheet metal cap sothat the amount of heat radiated onto the grid electrode 5, andparticularly the central area thereof, from the cathodeheatingarrangement, is kept small.

The grid electrode 5 is arranged above the cathode at a short distancefrom the emissive area 2, together with its mounting, essentiallycomprises a rigid cupped sheet metal cylinder, the active grid structureof which is in the end face where it takes the form of an annular slot 6which is crossed by radially-disposed grid elements. The grid elementspreferably consists of very narrow spokes, e.g., of flat rectangularcross-section. The Solid central part of the grid electrode, which ismade of a material having good thermal conductivity, provides anadditional heat balance in the neighborhood of the grid elements.

When the tube is constructed as a tetrode, an additional, cupped gridelectrode is provided beyond the control grid 5 to act as a screen grid.By providing cooling fins on the connecting portion of this electrode,highly effective heat dissipation from the screen grid is achieved.

The hollow anode 7 comprises a cupped hollow cylinder closed off at itsopen end by a substantially rigid diaphragm '8 which is interrupted byan annular slot 9 which may be provided with radial spokes forstiffening. When the tube is in operation, it is at this diaphragm thatthe high-frequency energy carried by the hollow electron beam is pickedoff. Any stiffening spokes in this annular diaphragm and the gridelements of the control grid or control and screen grids, are alignedwith each other so that they are virtually completely untouched by thehollow electron beam emitted from the annular area of the cathode andfocused by a magnetic field. The solid parts of the anode end face, thusremain untouched by the hollow electron beam as the latter passesthrough the tube in the course of its discharge, i.e., the end faceexperiences virtually no electron bombardment, while behind the end facethe hollow beam is fanned out radially and is incident upon the largeinternal wall area of the cylinder.

The focusing of the hollow electron beam is effected either as shown bya coil 11, which is encapsulated in the magnetic material, or by acorresponding permanent magnet ring. The magnetic flux is conducted byway of the magnetic material 12 in such a way that the requisite fieldis developed, or is'present, in the discharge space.

The cooling of the anode 7 is effected with the help of a multi-passageair cooler 13 and an air distributor 14 associated with the gridelectrodes, preferably by using an air stream directed onto the junctionor connection points.

The tube is made to form part of a single unit together with the coolingdevice 13, 14, and an associated tank circuit 15 provided with acorresponding tuning device 16. I

In the metal-ceramic tube, individual ceramic cylinders 17, 18 areresponsible for insulating anode and cathode circuits, respectively, andafter the required metalizing for connection are connected with therelevant metal cylinders or electrode parts, for example by brazing.

All of the parts in the neighborhood of the magnetic focusing componentsare constructed of magnetic material, unless requirements dictateotherwise.

The design of a tube in accordance with the present invention hasconsiderable advantages because the high current density achieved makesit possible to obtain extremely steep gain characteristics and thereforehigh gains. Critical factors in achieving this result are themagnetically focused hollow electron beam, the enlarged impact area onthe hollow anode and the relatively solid grid electrode with its innerpart of a material having good thermal conductivity.

Although we have described our invention by refer ence to a specificpreferred embodiment thereof, many changes and modifications of ourinvention may become apparent to those skilled in the art withoutdeparting from the spirit and scope of the invention. We thereforeintend to include within the patent warranted hereon all such changesand modifications as may reasonably and properly be included within thescope of our contribution to the art.

What we claim is:

l. A disc-sealed electron discharge tube, comprising: a cathode foremitting a hollow electron beam; a hollow anode including a flat surfacehaving an annular slot for passing the hollow electron beam and anarcuate surface for receiving the hollow electron beam; and at least onegrid electrode disposed in the path of said hollow electron beam andincluding a solid central part, means defining an annular slot forpassing the hollow electron beam, said flat surface of said anode andsaid means defining an annular slot of said grid each including aplurality of radial elements extending spokelike across said annularslots and aligned with the radial elements of each other; and means formagnetically focusing the hollow electron'beam to fan out the beam onlywithin said hollow anode.

2. A tube according to claim 1, wherein said hollow anode comprises ahollow cylinder which extends beyond said flat surface, and convectioncooling means associated with said hollow cylinder.

3. A tube according to claim 1 wherein said grid electrode is cup-shapedand has a surface disposed about said cathode and extending away fromsaid anode.

4. A tube according to claim 1 comprising a screen grid having a solidcentral portion, means defining an annular slot therein for passing thehollow electron beam, radial elements extending across said annular slotand cooling fins extending from said screen grid.

5. A tube according to claim 1, wherein portions of said electrodes andportions of said discharge tube, other than said cathode, consisting ofmagnetic material.

6. A tube according to claim 1 comprising an associated tank circuit anda cooling arrangement constructed together with said magnetic focusingmeans and said tube as a single unit.

t i I l '0'

1. A disc-sealed electron discharge tube, comprising: a cathode foremitting a hollow electron beam; a hollow anode including a flat surfacehaving an annular slot for passing the hollow electron beam and anarcuate surface for receiving the hollow electron beam; and at least onegrid electrode disposed in the path of said hollow electron beam andincluding a solid central part, means defining an annular slot forpassing the hollow electron beam, said flat surface of said anode andsaid means defining an annular slot of said grid each including aplurality of radial elements extending spoke-like across said annularslots and aligned with the radial elements of each other; and Means formagnetically focusing the hollow electron beam to fan out the beam onlywithin said hollow anode.
 2. A tube according to claim 1, wherein saidhollow anode comprises a hollow cylinder which extends beyond said flatsurface, and convection cooling means associated with said hollowcylinder.
 3. A tube according to claim 1 wherein said grid electrode iscup-shaped and has a surface disposed about said cathode and extendingaway from said anode.
 4. A tube according to claim 1 comprising a screengrid having a solid central portion, means defining an annular slottherein for passing the hollow electron beam, radial elements extendingacross said annular slot and cooling fins extending from said screengrid.
 5. A tube according to claim 1, wherein portions of saidelectrodes and portions of said discharge tube, other than said cathode,consisting of magnetic material.
 6. A tube according to claim 1comprising an associated tank circuit and a cooling arrangementconstructed together with said magnetic focusing means and said tube asa single unit.